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- Jones, G. H., et al.
(författare)
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The dust halo of Saturn's largest icy moon, Rhea
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 319:5868, s. 1380-1384
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Tidskriftsartikel (refereegranskat)abstract
- Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.
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| 2. |
- Morooka, Michiko, et al.
(författare)
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The electron density of Saturn's magnetosphere
- 2009
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 27:7, s. 2971-2991
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated statistically the electron density below 5 cm(-3) in the magnetosphere of Saturn (7-80 R-S, Saturn radii) using 44 orbits of the floating potential data from the RPWS Langmuir probe (LP) onboard Cassini. The density distribution shows a clear dependence on the distance from the Saturnian rotation axis (root X-2 + Y-2) as well as on the distance from the equatorial plane (vertical bar Z vertical bar), indicating a disc-like structure. From the characteristics of the density distribution, we have identified three regions: the extension of the plasma disc, the magnetodisc region, and the lobe regions. The plasma disc region is at L<15, where L is the radial distance to the equatorial crossing of the dipole magnetic field line, and confined to vertical bar Z vertical bar <5 R-S. The magnetodisc is located beyond L=15, and its density has a large variability. The variability has quasi-periodic characteristics with a periodicity corresponding to the planetary rotation. For Z > 15 R-S, the magnetospheric density distribution becomes constant in Z. However, the density still varies quasi-periodically with the planetary rotation also in this region. In fact, the quasi-periodic variation has been observed all over the magnetosphere beyond L=15. The region above Z=15 R-S is identified as the lobe region. We also found that the magnetosphere can occasionally move latitudinally under the control of the density in the magnetosphere and the solar wind. From the empirical distributions of the electron densities obtained in this study, we have constructed an electron density model of the Saturnian nightside magnetosphere beyond 7 R-S. The obtained model can well reproduce the observed density distribution, and can thus be useful for magnetospheric modelling studies.
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| 3. |
- Golding, H, et al.
(författare)
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CCR5 N-terminal region plays a critical role in HIV-1 inhibition by Toxoplasma gondii-derived cyclophilin-18
- 2005
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 280:33, s. 29570-29577
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Tidskriftsartikel (refereegranskat)abstract
- Molecular mimicry of chemokine ligands has been described for several pathogens. Toxoplasma gondii produces a protein, cyclophilin-18 (C-18), which binds to the human immunodeficiency virus (HIV) co-receptor CCR5 and inhibits fusion and infection of T cells and macrophages by R5 viruses but not by X4 viruses. We recently identified structural determinants of C-18 required for anti-HIV activity (Yarovinsky, F., Andersen, J. F., King, L. R., Caspar, P., Aliberti, J., Golding, H., and Sher, A. ( 2004) J. Biol. Chem. 279, 53635 - 53642). Here we have elucidated the fine specificity of CCR5 residues involved in binding and HIV inhibitory potential of C-18. To delineate the regions of CCR5 involved in C-18 binding, we analyzed C-18 inhibition of cells expressing CXCR4/CCR5 chimeric receptors and CCR5 with a truncated N terminus (Delta 2-19). These experiments identified a critical role for the N terminus of CCR5 in C-18 binding and anti-HIV activity. Studies with a large panel of CCR5 N-terminal peptides, including Tyr-sulfated analogues, truncated peptides, and alanine-scanning mutants, suggested that each of the 12 - 17 amino acids in the N terminus of CCR5 are essential for C-18 binding and inhibitory activity. Tyr sulfation did not improve C-18 reactivity. This finding is of interest because the same CCR5 N-terminal region was shown previously to play a key role in binding of HIV-1 envelope glycoproteins. The elucidation of the functional C-18-binding mechanism may help in the rational design of novel antiviral agents against HIV.
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| 7. |
- Öhrn, A., et al.
(författare)
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Calibration procedure for a neutron monitor at energies below 20 MeV
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 592:3, s. 405-413
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Tidskriftsartikel (refereegranskat)abstract
- A liquid scintillation detector aimed for neutron energy and fluence measurements in the energy region below 20 MeV has been calibrated using monoenergetic and white spectrum neutron fields. Careful measurements of the proton light output function and the response matrix have been performed allowing for the application of unfolding techniques using existing codes. The response matrix is used to characterize monoenergetic neutron fields produced by the T(d,n) reaction at low deuteron energies.
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